Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) (http://emc.medicines.org.uk), or the British National Formulary (BNF) (www.bnf.org).

• Cetirizine, fexofenadine, or loratadine (once-daily non-sedating antihistamines) are recommended for the treatment of urticaria.
• If an additional sedating antihistamine is needed for night-time use, if the itch is interfering with sleep, chlorphenamine or hydroxyzine are recommended.

• Non-sedating antihistamines are routinely increased beyond the recommended licensed dose in secondary care to control symptoms. It is not advisable to increase above the maximum licensed dose unless the healthcare professional has experience in doing so, or before seeking specialist advice.

• Antihistamines (H₁-receptor blockers) are the only drugs licensed for use in urticaria.
• Although the efficacy of antihistamines has only been demonstrated for chronic urticaria, there is a consensus that they are also effective for acute urticaria [Grattan et al, 2001; Zuberbier et al, 2006]:
• Histamine is one of the primary mediators of urticaria.
• In people with chronic urticaria, randomized controlled trials of non-sedating antihistamines have demonstrated improvements in symptoms of itch, weal formation, frequency of exacerbations, and quality of life [Belaich et al, 1990; Breneman et al, 1995; Kaplan et al, 2005; Zuberbier et al, 2006].
• Non-sedating antihistamines should therefore be used initially to control daytime symptoms.
• Sedating antihistamines are not recommended for daytime use because the drowsiness they cause can affect a person's ability to drive or perform other skilled tasks [Grattan et al, 2001; Zuberbier et al, 2006]. However, the addition of a sedating antihistamine at night to a non-sedating (daytime) antihistamine may help people who are unable to sleep due to itching, and is considered to be safe [Grattan et al, 2001].
• Desloratadine (a metabolite of loratadine) and levocetirizine (an isomer of cetirizine) are more recently marketed products, but there is little evidence to confirm whether they confer any additional benefit over the more established non-sedating antihistamines [MeReC, 2004].
• Mizolastine has been implicated in causing an abnormal prolongation of the QT interval and is therefore not recommended as a first-line treatment.
• Acrivastine is not recommended as it has a short half-life and needs to be taken three times a day.

• Where possible, oral antihistamines should be avoided during pregnancy, especially during the first trimester.
• If an oral antihistamine is required to control urticaria or pruritus during pregnancy, chlorphenamine is the antihistamine of choice.
• Loratadine and cetirizine are recommended for use during breastfeeding.

• Chlorphenamine is not licensed during pregnancy, but there have been several thousand known exposures with no evidence of an increased risk of fetal toxicity.
• The safety of other oral antihistamines in pregnancy has not been established. The available evidence does not suggest that other antihistamines (sedating or non-sedating) are associated with a high risk of teratogenic effects, but there are not enough documented exposures to be confident that there is no risk or only a very low risk of fetal malformations.
• Loratadine and cetirizine are preferred during breastfeeding as only small amounts are secreted in breast milk and both drugs are non-sedating.

[Lee et al, 2000; DTB, 2002a; NTIS, 2002; UKMiCentral, 2004]

• Sedating antihistamines cause sedation in 10–50% of people, which can persist into the next day [DTB, 2002a].
• Most non-sedating antihistamines have the potential to cause sedation, especially at higher doses. Advise people taking non-sedating antihistamines that they may cause sedation, and that the sedative effects are enhanced when combined with alcohol.

• Adverse effects are uncommon with occasional, short courses of oral corticosteroids.
• If frequent courses of oral corticosteroids are needed, the following monitoring is recommended:
• People taking frequent courses of oral corticosteroids require specialist supervision.
• Blood pressure: monitor regularly and treat if necessary.
• Diabetes mellitus: screen regularly and treat if necessary.
• Osteoporosis: see the CKS topic on Osteoporosis - preventing steroid-induced for details about when to prescribe long-acting bisphosphonate therapy.
• Growth suppression: record height of children regularly and accurately.
• Cataracts: screen children periodically.
• Children who are on frequent courses of oral corticosteroids should have regular checks for signs of adrenal suppression, with referral to a paediatrician who can arrange synacthen testing where appropriate.